about mechanism of CTS ??
After cts tracing the clock path, cts will divide many steps to do local cts (then use macro model to do cts upper level) from Sinks up to source clock as below for example:
**** CK_START: Update Database (mem=3265.2M)
36 Clock Buffers/Inverters inserted.
**** CK_END: Update Database (cpu=0:00:00.0, real=0:00:00.0, ...